When we re-finished our hardwood floors several years ago, the varathane bubbled after application and the bubbles dried in it. We had to have our floors professionaly refinished (at Varathane's expense... they said we got a bad batch)

Now I'm terrified of trying the other 3 rooms and hallway. Is polyurethane usually this difficult to work with?

We did the work in June/July -- 80s outside, but since we're high desert, probably 15-20% humidity. Will that make a difference? I'd really like to do these other rooms but am concerned about bubbling again.